Help with an iPhone 4?

This phone has been part of the family for a few years now. My sister is getting it on her birthday, and when my dad and I was looking through it, we noticed there was restrictions it. He can't remember what the password is, its been years since we opened it again. We tried reseting the whole phone, so it was brand new, but it kept asking for the restrictions password. Is there a way to reset it without the pass?

Enter DFU mode - https://www.theiphonewiki.com/wiki/DFU_Mode

From there you can restore via iTunes on a computer without needing the password.